It's not that easy for me to argue in a foreign langage, so forgive me if this is not very clear.

If I understand correctly, what you are describing is HSM (high speed machining).

There are now other roughing strategies (trochoidal milling for example) that allow cutting at high speed with a high pass depth. I cut HDU board up to 30lb/ft3 with a 1/2" end mill, 45% stepover, 2" pass depth at 50 ft/mn*. After each main Z pass, the software cuts again this pass with several small Z steps. Which means these shallow cuts only require cutting along the previous cut. So I finally get shallow cuts after removing quickly raw material and I can run 3D finishing at full speed.

Again, this software (CAM only, no CAD) costs me much more than Aspire which is worth every cent. I did not bought another software because I was not happy with Aspire. I already had this software for jobs that are very different than bas-relief and bought Aspire later. Aspire tool path (including finishing) are not well suited for models with high slopes, but it's not its first goal.

* for those who use a coherent units system : 480kg/m3 HDU, 12mm end mill, 50mm pass depth at 250 mm/s

dealguy11 wrote: It's hard on the spindle, hard on the bit, and risks yanking the material out of whatever work holding system you're using.

You're perfectly right Steve, and I strongly agree.

These are exactly the issues you have with a software which is not designed for this. That's why I bought a costly software which finely tunes lead modes, the actual stepover, and other parameters. It also offers much more finishing strategies than Aspire.

We can't afford machining slowly when producing rather large parts (up to 2x3m - 6.6x9.8 ft).

But I admit my remark was a little off-topic as Aspire tool path are not bad at all for bas-relief, its main goal.

If I understand correctly, what you are describing is HSM (high speed machining)."

Actually, I was not. I was referring to the OP's question about the validity of the technique of using Vectric's "Z Level" roughing toolpath to remove material prior to running a 3D relief file on a shallow model. Most likely in wood. Many, maybe even most, of the features you mention are not available in the software titles discussed here. All units of measure are coherent, there is usually a simple formula to calculate between them. Its all in what you grew up with.